Electrical loads that require multi-pole control of electrical current, e.g. electric motors, are used in a variety of applications in industrial controls, motor vehicles and other devices. Industrial applications include, for example, robotics devices and electrically controlled pumps for chemical process systems. Vehicle applications may include, for example, electronic throttle control actuators and cruise control actuators. Often these motors are remotely mounted away from a load controller and a driver circuit, with a wiring harness providing electrical power connection. These devices often require diagnostic capabilities to detect fault conditions and to assist in troubleshooting problems and repairing the system.
A circuit for controlling an electric motor may also be used to monitor performance of the device. When a fault occurs in a circuit, the effect in an industrial setting is machine downtime and a resulting loss in productivity. The effect on a motor vehicle includes a loss in system performance, damage to related systems and components, or an increase in emissions of the vehicle. The increase in emissions has become important with the advent of government regulations that compel addition of on-board vehicle diagnostic systems to monitor emissions related components and control systems. The intent of the on-board diagnostic systems is to detect faults that lead to emissions increases.
There is a need to identify a specific location of a fault or malfunction once it has been detected to ensure that a fault is quickly located and effectively repaired. This need to identify the location of a fault is important to minimize a loss of productivity associated with machine downtime in a factory, or to minimize costs to diagnose and repair a system on a vehicle.
When a fault occurs in a system, there is a need to identify the type and location of the fault to facilitate repair. When a fault occurs on a vehicle a diagnostic fault indicator may be set. This fault indicator typically identifies the system wherein a fault has occurred, but lacks sufficient specificity to identify where a specific repair needs to occur. The diagnostic fault indicator leads a repair technician to a system whose performance may be affected by interactions between several components or subsystems. The technician may be compelled to work through multiple diagnostic procedures to locate and repair the fault. This consumes time and resources, and results in increased cost and decreased satisfaction to the vehicle owner. A further outcome may be that a diagnostic code leads a technician to replace a motor, when the needed repair was the replacement or repair in a wiring harness leading to the motor.
The ability to correctly detect and identify a fault is more difficult when the fault is intermittent, as may occur when there is water intrusion into a wiring harness or connector. A technician spends time and resources in attempting to reproduce fault conditions to identify a fault or verify a repair. This results in customer dissatisfaction and high costs to the customer or the manufacturer, due to multiple attempts to identify and repair intermittent faults in a circuit. This problem is apparent when a fault occurs that sets a general diagnostic code that lacks sufficient specificity to identify a needed repair.
Electrical wiring harnesses may include devices such as insulated wires, connectors, drive transistors or relays, wiring junctions, and fuses. There are also electronic devices available called ‘intelligent drivers’ or ‘intelligent switches’ used to drive a motor. A fault in the wiring harness that may lead to incomplete operation of an electric load system includes wiring harness shorts to ground, wiring harness open circuits, and wiring harness intermittent connections. Other faults include broken or abraided wires, and connector faults such as relaxation of terminals, or corrosion due to intrusion of water or contaminants.
There are standard methods existing to diagnose and repair faults using off-board techniques such as connectivity tests and diagnostic trouble trees. These methods and tools are contained in service manuals, and are well known in the art. Off-board techniques require the employment of intrusive test methods, including the use of hand held scan tools used by a skilled technician.
There are electronic devices available on the market today called ‘intelligent drivers’ or ‘intelligent switches’ that have the capability to detect some open circuit and short circuit conditions but not all the conditions covered by this invention. A significant improvement offered by this invention is that most open circuit and short-circuit conditions are detected before the circuit is activated and also suggest the location of the fault.
The prior art diagnoses faults in electrical load circuits on-board the vehicle through the addition of current-monitoring devices that add cost and complexity to the circuit. The prior art has also used the intelligent drivers and intelligent switches to detect some open circuit and short circuit conditions. The prior art also identifies the presence and location of faults with on-board intrusive methods and systems that send a signal through the circuit to the motor, and look for a subsequent output from the motor. Each of these methods is disruptive when occurring during normal operation of the vehicle or the system. The prior art also does not address the issue of identifying the presence of an intermittent fault in a circuit, and the related result of being able to focus the repair efforts of a technician to a specific location in the system. The prior art also does not provide any capability of detecting a fault prior to powering the motor. Other methods have been limited in the range of diagnostic capabilities. Hence, there is a need to identify and diagnose a malfunction in a wiring harness for a remote mounted motor, and to perform the diagnostic prior to activating the wiring harness.